AUTHOR=Sun Yao-Hui , de Jong Maarten F., den Hartigh Andreas B., Roux Christelle M., Rolan Hortensia G., Tsolis Renee M.

TITLE=The small protein CydX is required for function of cytochrome bd oxidase in Brucella abortus

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=2

YEAR=2012

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2012.00047

DOI=10.3389/fcimb.2012.00047

ISSN=2235-2988

ABSTRACT=<p>A large number of hypothetical genes potentially encoding small proteins of unknown function are annotated in the <italic>Brucella abortus</italic> genome. Individual deletion of 30 of these genes identified four mutants, in <italic>BAB1_0355</italic>, <italic>BAB2_0726</italic>, <italic>BAB2_0470</italic>, and <italic>BAB2_0450</italic> that were highly attenuated for infection. <italic>BAB2_0726</italic>, an YbgT-family protein located at the 3′ end of the <italic>cydAB</italic> genes encoding cytochrome <italic>bd</italic> ubiquinal oxidase, was designated <italic>cydX</italic>. A <italic>B. abortus cydX</italic> mutant lacked cytochrome <italic>bd</italic> oxidase activity, as shown by increased sensitivity to H<sub>2</sub>O<sub>2</sub>, decreased acid tolerance and increased resistance to killing by respiratory inhibitors. The C terminus, but not the N terminus, of CydX was located in the periplasm, suggesting that CydX is an integral cytoplasmic membrane protein. Phenotypic analysis of the <italic>cydX</italic> mutant, therefore, suggested that CydX is required for full function of cytochrome <italic>bd</italic> oxidase, possibly via regulation of its assembly or activity.</p>